This invention relates generally to sonar apparatus and more particularly to low frequency sonar apparatus which can penetrate the bottom of a body of water and detect sub-bottom targets.
It has become common practice to bury cables and pipelines to avoid damage due to bottom fishing activities and anchors and as a result there is a need to detect disabled cables and pipelines for repair.
It is well known that low frequency sonar operating below 40 kHz can penetrate the sea bottom and detect buried objects; however, in present state-of-the art systems, the apparatus used to detect a buried cable results in an excessive false alarm rate which makes detection of linear targets such as cables and pipelines, very difficult, if not impossible.